U.S. Pat. No. 7,097,516 B2 discloses a connecting box for a solar panel comprising a housing having an opening for introducing contacts of the solar panel; contact elements provided in the housing for electrically connecting to the contacts of the solar panel, the contact elements having a tapered receiving region and a contact region extending from the tapered receiving region for automatic introduction of a contact of the solar panel via the receiving region into the contact region; and a base board for receiving the housing, the base board having an opening positioned along the opening of the housing, and the housing having a receiving space for insertion of the contact being laterally offset from a lid opening. The contact region has a front receiving region and a lower receiving region. In the front receiving region, there are two spring arms bent outwards, so that the front receiving region tapers in the direction of the contact region. The two spring arms are also arranged at an acute angle to one another in the lower receiving region, so that the lower receiving region tapers from the bottom. With these arrangements, a fixed contact at one end of a solar panel can be automatically inserted into the contact region from below and from the front and be clamped in place by the two spring arms.
In the connecting box for a solar panel disclosed in U.S. Pat. No. 7,097,516 B2, the fixed contact at one end of the solar panel is clamped in place by the two spring arms in the contact region. However, the two spring arms clamp the fixed contact only from left and right sides or upper and lower sides of the fixed contact. The clamping force can be applied by the two spring arms to the fixed contact at one end of the solar panel appears to be insufficient for firmly holding the fixed contact, and the two spring arms tend to deform at their bent areas after having been used for a period of time due to repeated insertion and extraction of the fixed contact into and from the two spring arms. Under this condition, a clearance between the spring arms is increased, and the spring arms would fail to firmly clamp on the fixed contact at one end of the solar panel to thereby largely adversely affect the electric transmission performance of the connecting box.